Domestic and foreign critics had lambasted Americans for their hypocrisy in calling themselves a beacon to human freedom while only a few states moved on the slavery question.
Some southern antifederalists like Patrick Henry, most concerned about local control, tried to argue that any stronger government would eventually threaten slavery, but the more persuasive voices in the South were those like Charles Pinckney, who testified upon returning to South Carolina that he couldn’t imagine a better bargain could have been made for the planters. Much of what we know of the Constitutional Convention comes from his notes—which, recent scholarship suggests, he carefully edited for a posthumous audience.
He made sure, for example, that posterity would know that he objected to the slave trade being guaranteed for another 20 years—but this was a common Virginia position at the time, since Virginians were already net sellers of slavers rather than importers by 1787. When it came time to deal with the matter of slave representation in Federalist 54, Madison obliquely distanced himself from the three-fifths clause by saying that one had to admit that slaves were, irrefutably, both people and property.
He put the defense of the proslavery clauses in the voice of a Virginian and then called them “a little strained,” but just.
When we see things like this in today’s politics, we call it damage control.